I don't know if this was intended by the original author or not, but monsters spawning in Mushroom Islands is a violation of one of the hidden rules of Minecraft: no hostiles should spawn there.

It's already crazy that they spawn in the end as much as they do, really spices up that dimension. But I think some control over what biomes and dimensions they're allowed to spawn in would be nice.

Thanks for another issue report! Nether, end and mushroom biomes were never intended, the checks were just wrong.